Question

I need a function, native or user made, that checks if a string is a valid directory name.
I’ve had a look through the PHP documentation and I can only find the function is_dir which checks if it’s an existing directory or not and not a valid name for a directory.

Answer 1

This should work for you.

See regex for validating folder name & file name

if (strpbrk($filename, "\\/?%*:|\"<>") === FALSE) {
  /* $filename is legal; doesn't contain illegal character. */
}
else {
  /* $filename contains at least one illegal character. */
}